A method of controlling a servo motor for driving a feed axis through a control circuit in which cascade-connection is formed by providing a velocity feedback loop inside the position feedback loop, has thus far been known (for example, as disclosed in Patent Literature 1). The method according to PTL 1 includes calculating a predicted processing load on the basis of processing data such as the shape of a work, a processing instruction based on a processing program, and a position command, and adding the predicted processing load as predicted load command to an acceleration command to be outputted to a servo amplifier, in order to cope with a delay of the servo control unit arising from load fluctuation during the processing.